5 Foot Topographic Contours of Loudoun County, VA (2009)

Metadata:

• Identification_Information
• Data_Quality_Information
• Spatial_Data_Organization_Information
• Spatial_Reference_Information
• Entity_and_Attribute_Information
• Distribution_Information
• Metadata_Reference_Information

Identification_Information:

Citation:

Citation_Information:

Publication_Date: 20101115

Title: 5 Foot Topographic Contours of Loudoun County, VA (2009)

Geospatial_Data_Presentation_Form: vector digital data

Description:

Abstract:

Elevation contours are a base map data layer derived by automated processes and processed for cartographic representation at 1:2400 scale. The line features represent the 5' contour intervals, 25' and 100' index contours as mapped from above and are mapped to National Map Accuracy Standards (NMAS).

Purpose:

In 2010, the 5' Topographic Contours dataset was "replaced" by a new 4' Topographic Contours dataset that Loudoun County received from an agreement with Virginia Geographic Information Network (VGIN). Loudoun County OMAGI received the new countywide dataset as a result of contributing to VGIN's contract. The 5' Contour Dataset is no longer used in OMAGI's County Basemap updates.
Topography is used by both the private and public sectors for utility and stormwater planning and site design. It has many other uses as well, including agricultural planning. Topography is an essential component in the maintenance of the floodplain data.

Supplemental_Information:

2009 was the last year that this 5' topographic dataset was updated.
OMAGI updates all base map data via a photogrammetric process, using aerial imagery that is flown yearly in phases. A different portion of the County is updated each year with the base map maintenance services contract, depending upon development patterns and update funding. See "Lineage" section for the list of extents for each Phase area, which are listed as “Data Sources”. The field “UPD_DATE” indicates the date a feature was last re-mapped, although it may have been reviewed for changes more recently. For a map of the most recent reviews and updates within the county, please see (insert a link to a Flickr map).
Data are stored in the corporate ArcSDE Geodatabase as a line feature class. The coordinate system is Virginia State Plane (North), Zone 4501, datum NAD83 HARN, Vertical datum, NAVD88, US Survey foot units.

Status:

Maintenance_and_Update_Frequency: Annually

Spatial_Domain:

Bounding_Coordinates:

West_Bounding_Coordinate: -77.964543

East_Bounding_Coordinate: -77.313965

North_Bounding_Coordinate: 39.329742

South_Bounding_Coordinate: 38.836941

Keywords:

Theme:

Theme_Keyword_Thesaurus: None: Employee generated

Theme_Keyword: Topography, Elevation, Conturs, Terrain, Surface, Topo

Theme:

Theme_Keyword_Thesaurus: ISO 19115 Topic Categories

Theme_Keyword: elevation

Place:

Place_Keyword_Thesaurus: None: Employee generated

Place_Keyword: Virginia, Loudoun, County

Access_Constraints: None

Use_Constraints:

These data were generated for use by Loudoun County and are available to the public. These data are intended for use at 1:2400 scale or smaller. Acknowledgement of Loudoun County would be appreciated in products derived from this data.

Point_of_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County, VA, OMAGI

Contact_Position: Base Map Coordinator

Contact_Address:

Address_Type: mailing and physical

Address: 1 Harrison Street SE, 2nd Floor

Address: MS 65

City: Leesburg

State_or_Province: VA

Postal_Code: 20175

Contact_Voice_Telephone: (703)771-5778

Contact_Facsimile_Telephone: (703)771-5075

Contact_Electronic_Mail_Address: mapping@loudoun.gov

Hours_of_Service: 8:00-4:30 EST, M-F

Point_of_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County, VA OMAGI

Contact_Position: Basemap Coordinator

Native_Data_Set_Environment:

Microsoft Windows Server 2008 Version 6.0 (Build 6002) Service Pack 2; ESRI ArcGIS 10.0.5.4400

Data_Quality_Information:

Lineage:

Source_Information:

Source_Citation:

Citation_Information:

Publication_Date: 20020304

Title: Base Map Maintenance Services Contract, QQ-00986, Phase I

Source_Scale_Denominator: 2400

Type_of_Source_Media: None

Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-00986, Phase I

Source_Contribution:

Captured Western 2/3 of County generally located north of Leesburg, west of Rt. 621, Evergreen Mills Rd, and south of Braddock Rd.

Source_Information:

Source_Citation:

Citation_Information:

Publication_Date: 20040308

Title: Base Map Maintenance Service Contract, QQ-00986, Phase II

Source_Scale_Denominator: 2400

Type_of_Source_Media: None

Source_Citation_Abbreviation: Base Map Maintenance Service Contract, QQ-00986, Phase II

Source_Contribution:

Captured Eastern 1/3 of County generally located to include Leesburg, east of Rt. 621, Evergreen Mills Rd, and north of Braddock Rd.

Source_Information:

Source_Citation:

Citation_Information:

Publication_Date: 20050303

Title: Base Map Maintenance Services Contract, QQ-00986, Phase III

Source_Scale_Denominator: 2400

Type_of_Source_Media: None

Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-00986, Phase III

Source_Contribution:

Captured photogrammetric stereo models covering highest development areas in the original Phase I region and including Leesburg.

Source_Information:

Source_Citation:

Citation_Information:

Publication_Date: 20070305

Title: Base Map Maintenance Services Contract, QQ-00986, Phase IV

Source_Scale_Denominator: 2400

Type_of_Source_Media: None

Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-00986, Phase IV

Source_Contribution:

Captured and updated photogrammetric stereo models covering highest development areas in the original Phase II region.

Source_Information:

Source_Citation:

Citation_Information:

Publication_Date: 20080303

Title: Base Map Maintenance Services Contract, QQ-01407, 2008

Source_Scale_Denominator: 2400

Type_of_Source_Media: None

Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-01407, 2008

Source_Contribution:

Captured and updated photogrammetric stereo models covering highest development areas in the north eastern region.

Source_Information:

Source_Citation:

Citation_Information:

Publication_Date: 20090302

Title: Base Map Maintenance Services Contract, QQ-01407, 2008

Source_Scale_Denominator: 2400

Type_of_Source_Media: None

Source_Citation_Abbreviation: Base Map Maintenance Services Contract, QQ-01407, 2008

Source_Contribution:

Captured and updated photogrammetric stereo models covering highest development areas in the western region.

Process_Step:

Process_Description:

Aerial film was acquired and imaged in 2002 (Virginia Base Mapping Program (VBMP) color) and 2004 (Loudoun County annual aerial mission (black & white). The imagery was scanned at 21 microns. Ground control used to support the compilation and was collected by identifying strategic locations on the aerial photography plan and then determining the coordinates by GPS ground survey techniques. The Aerial Triangulation was performed using softcopy workstations. Bundle adjustment was performed and Digital Elevation Models were created using and planimetric data were collected using standard photogrammetric collection techniques for breaklines and masspoints on soft copy workstations. Five foot contours were then generated from the compiled elevation data. Final deliverables in ESRI Interchange (E00) file format were placed on CD for delivery to OMAGI.

Process_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County, VA, OMAGI

Contact_Position: Base Map Cartographer

Process_Step:

Process_Description:

Each of the Base Map Data Layer coverages in the 27 delivery blocks comprising Phases I and II were loaded into a single Geodatabase Feature Class using ArcGIS Simple Data Loader. The entire feature class was then dissolved using ArcToolBox Dissolve, such that any adjacent features with identical values in all attributes consolidated into one feature. Record Counts, Frequencies, Length or Area summaries and final Topology checks were performed throughout the conversion procedure to ensure that multiple coverage data input matched single feature class data output (per TYPE code). To meet satisfactory QA/QC requirements the input coverage and output feature class must have the same record total, and on a record by record basis, area, perimeter and length differential of less than +/- 0.5%

Process_Date: 20050307

Process_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County, VA, OMAGI

Contact_Position: Base Map Cartographer

Process_Step:

Process_Description:

1. Legacy PGDB converted to DWG file. 2. DWG File imported to Microstation V8, and overlaid with the Update Parcels DGN. Identified Areas to be corrected. 3. Remap area inside parcel change layer a. If no change is detected the entities are not modified b. If new features are found they are collected as per the specifications c. If there is difference in shape or size of the planimetric, environmental or topographic features these are modified and coded as Update_Date = '2005' 4. Review remainder of model area outside the parcel change area a. If new features found they are collected as per the specifications 5. Updated Plan data in the Parcel areas have been checked for Edge matching 6. DTM was modified in the 11 major update areas 7. Contours were generated and edge matched with the legacy contour data 8. Checked contour coding at all the new buildings. 9. Checked the updated data on Ortho for completeness 10. All clean up tools have been run 11. Exported to Coverages and then to GDB. 12. Split the Area wise GDB into manageable pieces 13. Run QA/QC on each part of the Area wise GDB 14. Errors marked in the Log file have been corrected in the merged database 15. Merged the different Areas data into a single GDB i.e., Pilot, Areas 1, 2, & 4 16. Dissolved the polygons with same feature codes 17. Clipped legacy data to Phase 3 delivery boundary 18. Loaded new Phase 3 data and merged with existing Legacy data in east. 19. Loaded complete data sets (11) to enterprise SDE geodatabase

Process_Date: 20050314

Process_Step:

Process_Description:

1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be remapped. 3. New features were collected as per the data dictionary and the features that do not exist on 2007 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2007'. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against Orthos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Legacy PGDB was clipped to Phase 4 delivery boundary. 16. Updated Data was merged with the Legacy data. 17. Countywide complete dataset (11 layers) was loaded to enterprise SDE Geodatabase.

Process_Date: 20070604

Process_Step:

Process_Description:

1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be updated. 3. New features were collected as per the data dictionary and the features that do not exist on 2008 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2008'. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against Orthos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Updated Data was merged with the Legacy data. 16. Countywide complete dataset (11 layers) was loaded to enterprise SDE Geodatabase.

Process_Date: 20090907

Process_Step:

Process_Description:

1. Legacy PGDB converted to DWG file. 2. DWG file imported to micro station V8 and overlaid with the area to be updated. 3. New features were collected as per the data dictionary and the features that do not exist on 2009 imagery were deleted. 4. Modifications were done if there was a change in the shape and size of the features. 5. All the new and updated features were modified and coded as Update_Date= '2009'. 6. Updated data was checked for edge matching. 7. DTM was modified in the update area. 8. Contours were generated, coded and edge matched with the legacy contour data. 9. Spot Elevation Points were placed. 10. All clean up tools were run. 11. Data was exported to PGDB. 12. QA/ QC Program was run and reported errors were corrected. 13. Updated data was checked against 2009 Orthos for completeness. 14. All the delivery blocks were merged into a single PGDB. 15. Updated Data was merged with the Legacy data. 16. Countywide complete dataset (11 layers) was loaded to enterprise SDE Geodatabase.

Process_Date: 20101004

Spatial_Data_Organization_Information:

Direct_Spatial_Reference_Method: Vector

Point_and_Vector_Object_Information:

SDTS_Terms_Description:

SDTS_Point_and_Vector_Object_Type: String

Point_and_Vector_Object_Count: 430030

Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition:

Planar:

Map_Projection:

Map_Projection_Name: Lambert Conformal Conic

Lambert_Conformal_Conic:

Standard_Parallel: 38.03333333333333

Standard_Parallel: 39.2

Longitude_of_Central_Meridian: -78.5

Latitude_of_Projection_Origin: 37.66666666666666

False_Easting: 11482916.66666666

False_Northing: 6561666.666666666

Planar_Coordinate_Information:

Planar_Coordinate_Encoding_Method: coordinate pair

Coordinate_Representation:

Abscissa_Resolution: 0.00020833333333333297

Ordinate_Resolution: 0.00020833333333333297

Planar_Distance_Units:

Geodetic_Model:

Horizontal_Datum_Name: D North American 1983 HARN

Ellipsoid_Name: GRS 1980

Semi-major_Axis: 6378137.0

Denominator_of_Flattening_Ratio: 298.257222101

Entity_and_Attribute_Information:

Detailed_Description:

Entity_Type:

Entity_Type_Label: GISDBB.GISBROW.TOPO_5FT_LINE

Entity_Type_Definition: Line feature class

Entity_Type_Definition_Source: ESRI

Attribute:

Attribute_Label: OBJECTID

Attribute_Definition: Internal feature number.

Attribute_Definition_Source: ESRI

Attribute_Domain_Values:

Unrepresentable_Domain:

Sequential unique whole numbers that are automatically generated.

Attribute:

Attribute_Label: TO_TELEV

Attribute_Definition: Elevation of individual contour arc in feet

Attribute_Definition_Source: Automatically generated

Attribute_Domain_Values:

Unrepresentable_Domain: 0 - 2000 feet of elevation change in Loudoun County

Attribute:

Attribute_Label: TO_SOURCE

Attribute_Definition: Source that created or edited feature class

Attribute_Definition_Source: Loudoun County

Attribute_Domain_Values:

Enumerated_Domain:

Enumerated_Domain_Value: See Entity and Attribute Detail Citation for Data Dictionary

Attribute:

Attribute_Label: TO_UPD_DATE

Attribute_Definition:

The date a feature was last re-mapped, although it may have been reviewed for changes more recently

Attribute_Definition_Source: Loudoun County

Attribute_Domain_Values:

Unrepresentable_Domain: User generated text

Attribute:

Attribute_Label: TO_UPD_USER

Attribute_Definition:

for public distribution. Internal User ID of editor creating or modifying a feature. Intended for track and audit features internally by County.

Attribute_Definition_Source: Loudoun County

Attribute:

Attribute_Label: SHAPE

Attribute_Definition: Feature geometry.

Attribute_Definition_Source: ESRI

Attribute_Domain_Values:

Unrepresentable_Domain: Coordinates defining the features.

Attribute:

Attribute_Label: TO_TYPE

Attribute_Definition: Classification of Topo Contour

Attribute_Definition_Source: Loudoun County

Attribute_Domain_Values:

Unrepresentable_Domain: See Entity and Attribute Detail Citation for Data Dictionary

Attribute:

Attribute_Label: DB2GSE.SdeLength(SHAPE)

Overview_Description:

Entity_and_Attribute_Overview: TO_TYPE: Designation of Contour type

Entity_and_Attribute_Detail_Citation:

code description ---- ------------------ 1 5' contour 2 5' depression contour (delineates a "sink" or depressed bowl) 3 5' indefinite contour (obscured by vegetation or temporarily disturbed surface) 4 5' indefinite depression contour 5 5' null contour (lies within a building footprint and beneath bridge or overpass decks)
6 25' index contour 7 25' index depression contour 8 25' index indefinite contour (obscured by vegetation or temporarily disturbed surface) 9 25' index indefinite depression contour 10 25' index null contour (lies within a building footprint and beneath bridge or overpass decks) 11 100' index contour 12 100' index depression contour (delineates a "sink" or depressed bowl) 13 100' index indefinite contour (obscured by vegetation or temporarily disturbed surface) 14 100' index indefinite depression contour 15 100' index null contour (lies within a building footprint and beneath bridge or overpass decks)

Entity_and_Attribute_Detail_Citation:

TO_SOURCE: Source that created or edited feature class code description ---- ------------------ 1 Legacy (pre 2002) 2 County 3 Contract

Overview_Description:

Entity_and_Attribute_Overview: TO_SOURCE: Source that created or edited feature class

Entity_and_Attribute_Detail_Citation:

Code Description
0 Unknown 1 Legacy (pre 2002) 2 County 3 Contract

Distribution_Information:

Distributor:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County, VA, OMAGI

Contact_Position: Public Information Counter

Contact_Address:

Address_Type: mailing and physical

Address: 1 Harrison Street SE, 2nd Floor

Address: MS 65

City: Leesburg

State_or_Province: VA

Postal_Code: 20175

Contact_Voice_Telephone: (703)771-5778

Contact_Facsimile_Telephone: (703)771-5075

Contact_Electronic_Mail_Address: mapping@loudoun.gov

Hours_of_Service: 8:00-4:30 EST, M-F

Distribution_Liability:

Chapter 54.1-402 of the Code of Virginia.
"Any determination of topography or contours, or any depiction of physical improvements, property lines or boundaries is for general information only and shall not be used for the design, modification, or construction of improvements to real property or for flood plain determination."

Standard_Order_Process:

Digital_Form:

Digital_Transfer_Information:

Format_Name: GDB

Format_Specification: ESRI Geodatabase Feature Class

Digital_Transfer_Option:

Offline_Option:

Offline_Media: dvd

Fees:

Loudoun County distributes spatial data in ArcGIS database or shapefile & DXF format for the cost of reproduction. Countywide spatial datasets may be purchased for $22 per DVD for up to 4.5 GB of data. There is a $100 surcharge to purchase countywide topography, and a $3 charge if the item is to be mailed. If the customer wants the data in DXF format and/or would like OMAGI to custom select specific geographic areas of the County, there is an additional $7 per 15 minute increment labor charge. Select aerial imagery is also available.

Ordering_Instructions:

Size limit: 4.5 GB. Visit our website at: <http://www.loudoun.gov/omagi>, click on "Loudoun County Mapping Documents & Order Forms." The "Forms" directory will lead you to custom & standard (countywide) data order forms. Hardcopy maps may also be available; please contact the Mapping Office Public Information Counter for more information regarding all data requests.

Metadata_Reference_Information:

Metadata_Date: 20130114

Metadata_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: Loudoun County, VA OMAGI

Contact_Position: Base Map Coordinator

Contact_Address:

Address_Type: mailing and physical

Address: 1 Harrison Street SE, 2nd Floor

Address: MS 65

City: Leesburg

State_or_Province: VA

Postal_Code: 20175

Contact_Voice_Telephone: (703)771-5778

Contact_Facsimile_Telephone: (703)771-5075

Contact_Electronic_Mail_Address: mapping@loudoun.gov

Hours_of_Service: 8:00-4:30 EST, M-F

Metadata_Standard_Name: FGDC Content Standard for Digital Geospatial Metadata

Metadata_Standard_Version: FGDC-STD-001-1998

Metadata_Time_Convention: local time

Metadata_Use_Constraints:

This metadata reflects the source Geodatabase format and specific elements may not apply if your data is exported to SHP, DXF, or .e00 products. User must be aware that changes to data schema occur during data export that may not be reflected in this metadata, which represents Loudoun County's corporate geodatabase. Acknowledgement of Loudoun County would be appreciated in the use of this metadata.